In a known design of a rolling drive (German Pat. No. 721 899), the driven carriage is the roll-band carriage, which transfers its movement through the roll bands on the one side and a rocker arm on the other side onto the roll-cam carriage which carries the workpiece spindle. The roll-cam carriage must in such machines cover a relatively large path during its back and forth movement in order to communicate to the workpiece the necessary rolling motion. Caused by the drive arrangement in the known design, the roll-band carriage must cover yet a larger path, which has unfavorable effects on the rolling behavior of the roll bands and thus on the rolling motion of the roll cam and thus on the workpiece with the consequence that the grinding result is not satisfactory.
The roll cam which is used in the known device does permit, due to the slide ring which is guided in the rocker arm, the working of gears with a pitch circle diameter which is substantially larger compared with the roll cam, whereas the working of gears with a pitch circle diameter which is smaller compared with the roll cam is only possibly limited, because the slide rings prevent the adjusting of a randomly small distance between the pole point of the rocker arm and the hinge point of the rocker arm on the roll-cam carriage. If, however, gears with a pitch circle diameter which is larger compared with the roll-cam diameter are primarily worked, then errors which are created from inexactnesses in the rolling motion of the roll cam are transferred corresponding with the diameter ratio enlarged onto the workpiece.
The known device has therefore not found a significant acceptance in practice, even if the principle, to be able to work with a roll cam of specific diameter gears with substantially random pitch circle diameters, permits a quick and primarily inexpensive changing of the gear-grinding machine from one pitch circle diameter to another pitch circle diameter. In other known gear-grinding machines, a separate roll cam with precisely the same diameter must be provided for each pitch circle diameter. This means nothing different in practice than that for almost each workpiece design, a special roll cam must be manufactured or obtained, since different workpieces, according to experience, only very rarely have exactly the same pitch circle diameter. The purchasing and storage expenses for the many small roll cams are significant.
The basic purpose of the invention, therefore, consists in further developing the rolling drive of the abovementioned type so that the mentioned disadvantages are avoided, that is, that a roll cam of specific diameter is sufficient in order to work gears within a range of different pitch circle diameters, which range is as large as possible, without causing the utilized rollcam diameter to generate negative effects on the machining quality, in particular on the concentricity exactness and the flank profile.
The purpose is inventively attained by providing the rolling drive, which has the characteristic of (1) the driven carriage being the roll-cam carriage and wherein the pole point (A) ofth rocker arm and the hinge point (C) on the roll-band carriage lie on the same side of the hinge point (B) on the roll-cam carriage, such that between the distance AB of the pole point (A) of the rocker arm from the hinge point (B) of the roll-cam carriage on the rocker arm and the distance BC of the hinge point (B) from the hinge point (C) of the roll-band carriage on the rocker arm, there exists the relationship AB=BC or (2) the driven carriage being the roll-cam carriage and wherein the pole point (A) of the rocker arm and the pole point (C) on the roll-band carriage lie on the same side of the hinge point (B) on the roll-cam carriage, whereby the distance AB between the pole point (A) of the rocker arm and the hinge point (B) of the roll-cam carriage on the rocker arm is smaller than or at most the same size as the distance BC between the hinge points (B,C) of the roll-cam carriage and of the roll-band carriage on the rocker arm. If the pole point of the rocker arm and the hinge point of the two carriages are arranged according (1) above, the gears can be worked with almost any kind of a pitch circle diameter, than those with a larger, same or smaller diameter than the one of the roll-cam diameter. Whereas, if the pole point of the rocker arm and the hinge points of the two carriages are arranged according to (2) above, then only those gears can be worked, the pitch circle diameters of which are at most only as large as the roll-cam diameter. This means that the roll cam which is being used corresponds in diameter with the pitch circle diameter which is determined by other parameters and is the largest that can be worked on the machine and by no means enlarges possibly occurring inexactnesses in the rolling motion of the roll cam, but are transferred corresponding with the diameter ratio only in a reduced manner onto the workpiece.
Gear-grinding machines, in which the roll-cam carriage is driven for movement back and forth transversely with respect to the roll-cam or workpiece axis, are known (German OS No. 24 59 033), however, in these machines it is necessary to provide for each pitch circle diameter of the gears which must be worked a separate roll cam of a suitable diameter.
The description introduction of German Pat. No. 721 899 mentions a rolling drive which is comparable with the subject matter of the invention, in which rolling drive the driven carriage is the roll-cam carriage and in which the pole point of the rocker arm and of the hinge point on the roll-cam carriage lie on the same side of the hinge point on the roll-cam carriage. The pole point of the rocker arm is arranged stationarily in this rolling drive. How the hinge points on the rocker arm are adjusted to different workpiece diameters can not be taken from this text area.
A further object of the invention is the provision of structure wherein the pole point and the hinge points, in particular the hinge point of the roll-cam carriage, do not hinder one another during a setting of the machine; thus the pole point and the hinge point of the roll-cam carriage can have the same distance from the hinge point of the roll-cam carriage.
A still further object of the invention is an advantageous arrangement of the pole points and the provision of an associated indicator in a manner which substantially further simplifies the setting of the machine.
A still further object of the invention is the provision of an advantageous arrangement of the hinge points on the two carriages, because tests have shown that the hinge points during a direct arrangement on the carriages require, because of the movement of the rocker arm, a shape of the carriages which is unfavorable with respect to manufacture.
A still further object of the invention is the provision of a simple possibility to feed the grinding disk to the workpiece flank which is to be worked or to move the grinding disk away from the flank. The provision of a split or divided adjusting carriage is of great importance because the feeding to or moving away movement is always referred to the pitch circle. It would also be concievable to produce this movement by extending or shortening of the first or the second guide rod. The expense which would be necessary for this would, however, be enormous, since the guide rods would move constantly with the roll-cam carriage back and forth.